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 A126716 Least i such that prime(i)*2^(10^n) -1 is prime. 0
 2, 3, 51, 657, 6255 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,1 LINKS Table of n, a(n) for n=0..4. EXAMPLE 3*2^(10^0)-1=5 prime so a(0)=2 since 3 is prime(2). 3*2^(10^1)-1=3071=37*83 composite, 5*2^(10^1)-1=5119 prime so a(1)=3, since 5 is prime(3). PROG (PARI) a(n) = my(i=2); while (!isprime(prime(i)*2^(10^n) -1), i++); i; \\ Michel Marcus, Sep 15 2019 CROSSREFS Sequence in context: A065646 A268251 A090508 * A355648 A347894 A362836 Adjacent sequences: A126713 A126714 A126715 * A126717 A126718 A126719 KEYWORD nonn,more AUTHOR Pierre CAMI, Feb 13 2007 STATUS approved

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Last modified July 13 08:08 EDT 2024. Contains 374274 sequences. (Running on oeis4.)